1. Technical Field
The present invention relates to a liquid ejecting apparatus. Particularly, the invention is effective when applied to a case where, in addition to a discharge voltage used for discharging ink droplets, a fine-oscillation voltage used for causing fine oscillation without discharging ink droplets is applied to heat liquid in a pressure generation chamber which corresponds to non-discharging nozzles.
2. Related Art
An ink-jet type recording head (also referred to as a recording head, hereinafter) in which ink droplets are discharged through a plurality of nozzle openings by using pressure owing to displacement of a piezoelectric element has been known as a representative example of a liquid ejecting head, for example. Also, an ink-jet type recording apparatus equipped with the ink-jet type recording head described above has been known as an example of the liquid ejecting apparatus.
In the case of a recording head applied to the ink-jet type recording apparatus described above, there is a tendency that the temperature of the ink in a pressure generation chamber corresponding to non-discharging nozzles, out of the plurality of the nozzle openings forming nozzle arrays, through which the ink droplets are not discharged is lower than the temperature of the ink in a pressure generation chamber corresponding to discharging nozzles through which the ink droplets are discharged. The reason for this is that the ink in the pressure generation chamber corresponding to the discharging nozzles is replaced and is subjected to heat-exchange due to heat energy converted from part of oscillation energy which is generated by driving of a pressure generation unit.
When the ink temperature varies as described above, a discharge property of the ink discharged through each nozzle opening, particularly, a weight variation of the discharged ink, is caused due to a viscosity variation of the ink, for example.
In recent years, high-quality and high-resolution have been required for a recorded matter. With the trend toward high-quality and high-resolution, a method in which, in addition to a driving signal used for discharging ink droplets, a fine-oscillation signal is applied to the pressure generation unit corresponding to non-discharging nozzles such that meniscuses are finely oscillated without discharging the ink, and thus heat is generated has been proposed.
In many cases of the fine-oscillation signal supply methods of the related art, a waveform of the fine-oscillation signal is determined such that as much energy as some percentage of the energy induced by a discharge driving signal is applied under consideration of the discharge driving signal. Accordingly, the fine-oscillation signal is not always appropriately generated, and thus it is difficult to say that a fine-oscillation driving signal is appropriate to any operation condition of the recording head.
Examples of patent literature in which the ink temperature difference between the non-discharging nozzles and the discharging nozzles is reduced by applying fine oscillation include Japanese Patent No. 3418185 and No. 3674248.
However, in the case of technology disclosed in Japanese Patent No. 3418185 and No. 3674248, a problem that the ink temperature is greatly affected by ambient temperature and this is particularly remarkable in the non-discharging nozzles is not sufficiently considered. In other words, in the case of the technology disclosed in Japanese Patent No. 3418185 and No. 3674248, the fine-oscillation signal is difficult to be optimized, with respect to the discharge driving signal while sufficiently considering the ambient temperature and the ink temperature, to allow the ink temperature of the non-discharging nozzles to be always matched to the ink temperature of the discharging nozzles as much as possible.
This problem is not limited to the ink-jet type recording head discharging ink but common to a liquid ejecting head discharging other liquids.